The present invention relates to a water purification system that incorporates an electrodeionization (EDI) device; and more particularly to a method of sanitizing the EDI device.
Electrodeionization generally refers to a process for purifying liquids by combining ion exchange resins, ion exchange membranes, and electricity to purify the liquids. The use of water purification systems has increased in many industries. In particular, pure water is used in many industrial processes. Some of these processes include: producing semiconductor chips, power plant operations, petrochemical applications and producing pharmaceuticals. Ion exchange resins, reverse osmosis (RO) filtration, and electrodialysis techniques have been used to reduce the concentration of ions in a liquid. EDI devices are now commonly used as RO post treatment to reduce the concentration of ions producing ultra-pure water.
An EDI device generally includes an internal chamber, within which alternating arrangements of cation permeable membranes and anion permeable membranes define compartments. The diluting compartments contain ion exchange resin particles, which are regenerated through electric field induced water dissociation. The concentrate compartments may contain ion exchange particles or inert plastic netting to maintain membrane separation, and allow water flow. An applied electric current induces ion migration from the diluting compartments through the ion exchange media and ion permeable membranes into the concentrating compartments. The liquid flowing through the concentrating compartments is discarded or partially recycled. The purified liquid flowing through the diluting compartments is recovered as demineralized liquid product.
Operation of the water purification system infects the EDI device with bacteria and other undesirable substances. A sanitization process is used to disinfect the EDI device. Some disinfecting methods involve passing a disinfecting solution, which may include a chemical, at a temperature sufficient to inactivate any microorganisms in the EDI device.
There are a few issues with known methods of disinfecting the EDI device. Known methods require external equipment (water supply, heating means, etc) to disinfect the EDI device. Chemical disinfecting solutions may contain chemicals that react with the active components in the EDI device. This may lead to component degradation and the decrease of the usable life of the EDI device. These issues add to the cost and complexity of the water purification system.
For the foregoing reasons, there is a desire for an improved method of disinfecting an EDI device. The method should reduce the need for external equipment and disinfecting chemicals.